Friday, September 30, 2011

Ministry of Education Maps of Plutonium and Strontium Show Wide Dispersion of Supposedly Heavy Nuclides

On September 30 the Ministry of Education and Science posted the blurry maps plotting the locations where plutonium and strontium have been detected.

(On the same day, September 30, the national government abolished the evacuation-ready zone between the 20 and 30 kilometer radius from the plant, "allowing" the residents to return.)

The Ministry's 10-page document is in Japanese only for now.

According to the Ministry, the survey for plutonium and strontium was carried out in early June to early July in 100 locations within the 80-kilometer radius from Fukushima I Nuclear Power Plant by government researchers. One location each in 59 municipalities within the 80-kilometer radius was picked, based on the air radiation level and the high population density. The remaining 41 locations were picked from within the 20-kilometer radius evacuation zones.

The Ministry claims it is the first time plutonium has been detected outside the plant, but all that means is that it is the first time a government ministry has admitted to the existence of plutonium outside the plant. As the readers of this blog already knows, as early as April the researchers were taking soil samples outside the plant and have them tested for plutonium and found it (see here and here).

The Ministry's conclusion is that the amount of plutonium is not that big to cause any alarm, and that they should focus more on the decontamination of cesium-134 and -137.

As for strontium, the Ministry does sound a bit more nervous. It says the ratios of radioactive strontium to cesium-137 in these locations were calculated; the ratios varied too much, indicating there was no correlation between the deposition of radioactive strontium and radioactive cesium. The Ministry will conduct further, more detailed study in locations that had higher strontium ratios.

Plutonium-238 (top number in the map), Plutonium-239+240 (bottom number):

Strontium-89 (top number in the map), -90 (bottom number):


Anonymous said...

okay, we allready knew but still...

...aaaah shit!

Atomfritz said...

It is revealing that they exclude the plutonium-241 isotope (half-life 14.29 yrs), as this decays into Americium-241 which is commonly regarded as extremely dangerous in comparison even to plutonium.

Also interesting is that they show only the strontium-89 contamination (half-life 50 days) and not the long-term relevant strontium-90 (half-life 28.9 yrs) contamination.

And, as the measurements were taken in the course of about one month, almost one half-life-time of Sr-89, the precision of the strontium map is very low, error margin near 50%.

At least they start to trickle out some data, three months (!) after the measurements.
Looks as if they would love to keep the more-worrying data classified.

Anonymous said...

Question: Why Is There Not Tremendous International Outrage Directed at The Japanese Government???????

Atomfritz said...

The Pu-241 thing is very important because in addition to its extremely high radiation the contamination with reactor plutonium results in Am-241 contamination that increases over a time of hundreds of years.

Typically the plutonium mix in reactors contains about 15% Pu-241, in contrast to weapons-grade plutonium that contains a maximum of 0.5%, usually way less.

As the 14-year half-life of Pu-241 is extremely short in comparison to the bulk of the other isotopes (many thousand years), by far the most radiation damage is caused by the fast-decaying Pu-241, making the effects of the other Pu isotopes almost negligible.

So we have to assume that there will be a BIG Americium-241 problem in Japan in addition to the, also still covered-up, Pu-241 problem.

Further reading about Pu isotopes:

Caveat Emptor said...

September 30, 2011 Otsu-City, Shiga Prefecture, not far from Kyoto, Japan ...

Even with the 500-kilometer-distance from Fukushima, one concerned university professor in September 2011 near Kyoto is measuring ground radiation where he lives in Otsu-City, Shiga Prefecture, at around .4 microsieverts/hour.

That is at least ten times higher than the 0.03 microsieverts/hour background level the Japanese government asserts.

Anonymous said...

Did TEPCO not state that these are heavy metals and they don't fly?

arevamirpal::laprimavera said...

@anon 3:37PM, I think it was mostly the government and government scientists and pro-nuke researchers who insisted that plutonium or strontium wouldn't fly because they are heavy.

Yosaku said...


Wow. Did TEPCO really say that? (Not that I would be surprised if they did--I have about zero faith in them.) Everything I've read says that these heavier isotopes don't fly as far and the data seems to bear this out.

Seriously, if anyone has a link to TEPCO, the government or government scientists actually saying that it doesn't fly, I'd love to have it and pass it around as more evidence of their ineptness.

gmoke said...

Thank you for reporting on this. I've been following some of the work of Safecast on citizens' radiation monitoring and was wondering what official mapping was being done.

Is there a source you know of for a detailed estimate of all releases to date?

Anonymous said...

If these numbers are the calculated concentrations by June 14, Sr-89 would have already decayed to 1/4 of the shown amounts? I mean, it's been two half lives. Sr-90 numbers sound low, but there is one point in Soma with 2,400 Bq/m2, and that area was never evacuated (I mean, they may have evacuated beacuse of the tsunami, I don't know)

I don't understand their logic to decide in which points the Plutonium concentrations are from the plant. Seems to be related to the ratio of Pu-238 to Pu 239 & Pu 240, but the highest concentration of those last two (15 Bq/m2) was detected in the south of Minami-soma and they assume it's not Fukushima related.

The numbers are low for what I expected after checking Yablokov's numbers for Chernobyl.

Anonymous said...

@Atomfritz, they are showing the Sr-90 contamination. Look at the text over the bottom map.

Anonymous said...

@gmoke. The estimates of the inventory were published by METI here and compared to the releases after the Hiroshima bomb: (Not sure about the dates they are counting)

Atomfritz said...

To get a clue of the probable Pu-241 contamination, let's assume the composition of the Fukushima plutonium being 60% Pu-239, 25% Pu-240 and 10% Pu-241.

Specific activities (according to Wolfram Alpha, rounded):
Pu-239: 2.3 GBq/g
Pu-240: 8.4 GBq/g
Pu-241: 3.85 TBq/g

My calculation:
2.3*60 =138
8.4*25 =210
3850*10 =38500

So the ratio will be about 38500 / (138+210) = 111.

So just multiply the combined Pu-239+Pu240 activity with a number like 111 to get the minimum amount of Pu-241 contamination.

So, if you have 15 Bq/m2 of Pu-239+Pu-240 then we can conservatively assume a Pu-241 contamination of at least 1650 Bq/m2 to around 2400 Bq/m2!

(By the way, as this sampling location west of Minami Soma is in the deepest-red area of Prof. Hayakawa's map, I cannot accept if they state the contamination is not from Fukushima, while withhelding data about the isotopic composition of the plutonium measurement samples)

If more mishaps happen in Fukushima like spent fuel pools cracking or running out of water, resulting in an unquenchable fuel fire then the numbers can become even worse than those in Russia/Ukraine.

Anonymous said...

@Atomfritz, how does that compare to the numbers of Chernobyl? Around half of the 30km radius was contaminated with more than 3,700 Bq/m2 of Pu 239 and Pu 240 Vs. 15 Bq/m2 which is the maximum detected in Fukushima.

Atomfritz said...

anon 5:59
Yes, you are right, thanks for hinting.
I am not sure how I mistook this. As I thought about how this could happen, I remember only Sr-89 mentioned in the text. Maybe I read an early version of the article before it was corrected? But I suppose I was just unattentive as I concentrated on the plutonium and not the strontium map.
Duh. *slapping myself* I need to be more attentive for sure.

Atomfritz said...

@ anon 6:37

The big problem is the spent fuel pools.
It will take many years until it is possible to empty them from the spent fuel that resembles several Chernobyl reactor cores.

If they run out of water, be it because of cracking or of failure to replenish the water for any reason, the fuel will heat up, eventually leading to a big, practically unquenchable fuel fire and possibly also recriticality.

Such would release a big cloud of radionuclides into the air. And, as there are not immense quantities of graphite additionally feeding the fire, the smoke plume wouldn't rise as high as in Chernobyl. And this would lead the contamination less wide dispersed, resulting in most of the fallout hitting Japan concentrated and not be diluted over vast areas of Europe and Asia like it happened at Chernobyl.

The consequences of this would be dire for not only Japan.

Anonymous said...

Maybe if we make a dome like in the simpsons movie and close that place......

Yosaku said...

Atomfritz [@2;38 PM],

I'm right with you through all but the last sentence of your comment. Your descriptions of the relative strength of isotopes are on target.

However, to then make the jump that there will be a "BIG" problem in Japan, you need to link this up to the data in the chart and explain how these amounts will become a "BIG" problem. Please do so.

And I don't mean to say that your assertion is wrong (it may very well be right!). But without taking this step, it is baseless.


Anonymous said...

@Yosaku, Why do you insist on "evidence" and "data" on the comment section? Sounds strange, as the Japanese government and TEPCO have been doing without them for so long and you insist the readers of a blog to give you evidence? Who are you anyway?

Yosaku said...


Sorry to be asking for evidence. I just want to know how I can use this information. I'm pretty sure Atomicfritz means it when he says there's a "BIG" problem, but I would like to know why.

As for who I am, I live in Tokyo and have a family, so I have a keen interest in all of this and take the radiation risk seriously.

And don't worry, I will not be coming to the defense of TEPCO or the government anytime soon. I think they have proven themselves completely inept, and I lost faith in them a long time ago (not that I had much to begin with!).

Finally, I comment here because this blog is an invaluable resource and many of the people who comment here know their stuff (such as Atomicfritz).

Yosaku said...

And yes, it's Atomfritz, not Atomicfritz. My apologies.

Yosaku said...


Just wanted to say thanks again for your recent post verifying your assertion. Great link!

One of the reasons I follow this blog is that you are great at linking your assertions. There is so much misinformation out there (on both sides), that this site is a welcome relief.

Atomfritz said...

@ Yosaku 10:07
Thank you for hinting at this.
Your criticism is completely valid.
Yes, this deserves a more-in-depth look.

Official release estimate of Pu-241 as of the Tepco press release of 8/23 (see was about 1.2E+12 Bq. As you need about 30.5 Bq of Pu-241 to decay to get 1 Bq of Am-241 this will result in about 4E+10 Bq of Am-241.

But this release estimate might become completely obsolete in case of spent fuel pool fire, reactor hydrogen explosion or a combination/chain reaction of such events.

There are reportedly several tons of plutonium (sorry I don't know the exact number) in the pools alone. So we can suppose there is at least 100kg of Pu-241. If only one percent of this would be released in to the air, this would be at least one kilogram, equivalent to about 4,000 TBq (or 4E+15 Bq Pu-241) mainly dispersed in the form of strongly radiating hot particles.
These in turn would become at least 1.35E+14 Bq of Am-241. If you'd distribute this evenly on 300,000 square kilometers of Japan this would result in a contamination of about 13,500 Bq/m2 of Pu-241, finally becoming 450 Bq/m2 Am-241.

Now let's look at the famous "Nuclear scout".
Look at this article:,2933,292111,00.html
Look at the photo of the guy. I somehow doubt that he did deliberately smear the Am-241 onto his skin for cosmetic reasons. I am more tempted to believe it just was a small part of the Am-241 he recovered from the smoke detectors that accidentally escaped out of his makeshift laboratory (he had no "professional" hot cell available) when he decided to restart his strange nuclear "career".

So this could illustrate very well the effect of small hot particles of Am-241 of a few tens of becquerels only. And this was only external radiation damage from particles on the outer skin. Just imagine the effects if that would be internal, intestinal contamination.

Sorry for this fast and cursory answer.
This americium problem really needs more independent in-depth examination.

Some more reading on Am-241:

Atomfritz said...

And, let's not forget the most important problem regarding the problem of finding out the true impact of alpha/beta emitters like Pu and Sr.

As they do not emit a penetrating gamma radiation field, you cannot find hotspots of these as easy like at gamma emitters as Cesium. Neither transportable counters, handheld or airborne, nor gamma cameras can be used to find these hotspots.

As the experience of Russia shows, it is common that a sample appears to be "clean" and a sample taken ten meters away can be found to be heavily contaminated.
So, as another commenter mentioned, it would be crucial to know the exact sampling locations, their characteristics (what was the samples, how and where were they taken?) and the criteria for exactly picking those few locations.

The consequence is that for strontium, the main hotspots could only be found by a very dense sampling raster, many samples per square kilometer.

Finding the Pu-241 hotspots will be easier in some years when part of it has become Am-241, conveniently detectable by the gamma radiation it emits additionally when it alpha-decays.

As there has been only a handful of samples of plutonium, it is well possible that there are big "hot areas" that will be "populated" with more than 3000 Bq/m2 Pu-241, finally ending up in 100 or more Bq/m2 Am-241.
And this already depends on the (unsafe) assumption that there exist no areas with significantly more than 15 Bq/m2 Pu-239+Pu-240.

So, even if no more mishaps with big releases happen, the situation could be quite serious, more than the maps suggest.

Anonymous said...

"So, even if no more mishaps with big releases happen, the situation could be quite serious, more than the maps suggest."

Or less. 100 samples is already a good preliminary study. I don't think after Chernobyl they had to look very hard to find samples of Plutonium thousands of times more contaminated than anything found in this survey, even the closest ones to the Fukushima plant.

Good for Japan, considering what it could have been.But then again, they could have had a good plan for total plant black-out and we wouldn't even know where Fukushima is.

arevamirpal::laprimavera said...

@Yosaku, you're welcome, but please stop insisting on providing links for you to any "assertion" and calling comments without links for you as baseless. That's sometimes akin to asking for a verifiable "link" to a comment "It's a sunny day today" or "the government is stupid". You can do your own research which is often quite easy to do if you want to verify for whatever reason.

Atomfritz said...

@ anon 7:47

"100 samples is already a good preliminary study."

Hmm, let's look closer.

Samples counted (according to map):
Outside 80km range: 4 samples, maximum one 9.2 Bq Pu239+240, thus at least 1000 Bq Pu-241
30-80km range: 22 samples, maximum one 12.2 Bq Pu239+240, thus more than around 1300 Bq Pu-241
20-30km range: 9 samples, maximum one 11 Bq Pu-239+240, so at least about 1200 Bq Pu-241
0 to 20km range: 13 samples, "best" one 15 Bq Pu-239+240 15 Bq, indicating at least 1650 Bq Pu-241

Total count of samples only 48, not 100 (though I may have missed one or two, as map is of bad resolution).
And, sample density extremely decreasing with distance.
Only four samples outside 80 km range, one of them with very high reading!

If anything, then this only indicates that this study was at most a preliminary superficial lookup and there is an urgent need to take many more samples (especially outside of the 80km range) before we can conclude with some certainty that Plutonium really "stays" in the immediate vicinity of the accident site.

In fact, due to the low density of sample "grid" we must be aware that we possibly have not yet seen a really "hot" hotspot.

And, as one of the "hottest" spots was found outside the 80km range, where only four samples were taken, we cannot dismiss the possibility that really "hot" hotspots can be found even further away, possibly even south of Tokyo.

This "study" opens up more questions than it answers and calls for a thorough survey with more than this few samples.

Yosaku said...


I do my own research and did look for this, but unfortunately couldn't find it.

And I don't mean to be prickly, but I was an engineer in a past life (having worked on remediating Superfund and RCRA sites in the USA, I've probably seen and dealt with environmental disasters that most people here haven't), and so I like my data and I really don't appreciate vacuous assertions and hearsay.

Again, though, I think you are doing a great job here, and this is by far the best assembly of up-to-date postings on the situation I have found.

Yosaku said...


Excellent post and thanks for taking the time. Much appreciated.

Anonymous said...

@Atomfritz, "Total count of samples only 48, not 100 (though I may have missed one or two, as map is of bad resolution)."

50 of each, strontium analysis and plutonium analysis.

"And, as one of the "hottest" spots was found outside the 80km range, where only four samples were taken, we cannot dismiss the possibility that really "hot" hotspots can be found even further away, possibly even south of Tokyo."

Which sampling location are you referring to? All the samples are from within the 80km range.

As for the distribution of Strontium and Plutonium after Chernobyl, the maps published by the IAEA in 1991 show this: (big file, better save it and open it outside of your browser). The density of the contamination 30km around the plant would have made it impossible to miss anything like that. Of course, the surveys have to continue, like MEXT says in the report.

Anonymous said...

Also,about the ratio of Pu-238 to Pu-239/240 from previous fallout (1961-1980):

Not an easy task to determined which contaminants are from Fukushima and which from historical fallout, specially in the case of Plutonium.

Atomfritz said...

anon 7:54

"Which sampling location are you referring to? All the samples are from within the 80km range."

Let's again take a closer look.

Indeed, I notice now there have not been any strontium measurements outside of the 80km zone.

Further I notice that many sampling locations of the both maps don't overlap at all, leading to the conclusion that, for some yet-unknown reason, it has been decided to use different sampling locations.

This makes it impossible to evaluate the fallout correlation between Pu and Sr. Intentionally?

Please take a look at the plutonium map first.
Look at northeastern Ibaraki.
Near the coast you find two sampling points, the one outside of the 80km range with quite a high contamination.

Now look at the strontium map.
There has been no strontium sampling in or even near Ibaraki.
And so on.


As I was focusing on the plutonium map I didn't take sufficient notice of this important detail you made aware of with your post.
Many thanks!

This again shows how important it would be to know the sample location selection criteria.
What actual samples have taken from where exactly? Soil? Asphalt? Sewer sludge? From top-hill or from there where water runs downhill, or pits where it colletcs? Etc.

Without these information it is quite difficult to draw a realistic picture of the contamination situation.
Even the possibility cannot be excluded that the sampling location and item selection criteria were aimed to get the lowest possible measurements, just to calm people down.

Some smart sort of "doctoring" maybe, without actually faking/forging measurements?

Anonymous said...

@Atomfritz "What actual samples have taken from where exactly? Soil? Asphalt? Sewer sludge?"

The survey is based on soil samples.

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